1. Field of the Invention
This invention relates to improvements in the design and use of disk drive suspensions to reduce to near extinction disk drive off-track errors, e.g. track misregistration errors (TMR), that have proved irremediable by conventional disk drive design and manufacturing execution.
Off-track motion, generally, and TMR specifically, herein refer to unwanted variances in the position and attitude of the slider gap from that desired. A slider is an aerodynamic body that carries a magnetic head in operating proximity to a rotating disk A slider gap is the space between the pole pieces of the slider-carried magnetic head. As part of a magnetic head, a gap can produce or sense magnetic fields. For convenience, the ensuing invention description will generally refer to the slider gap (inclusive of the read gap and the write gap) as the write gap, unless otherwise indicated.
Insufficiently addressed sources of off-track motion include reaction effects from seek movements of the suspension, sway vibration forces, and torsional vibration forces. These three main sub-components of TMR, off-track motion, or out-of-phase motion more specifically include:
1. In seek mode, the slider gap oppositely reacts to a command, e.g. initially goes left when the actuator/suspension combination is commanded right;
2. Sway vibrations of the actuator-suspension result in off-track oscillations when the actuator/suspension combination is commanded to hold stationary over the track; and,
3. Torsional vibrations of the actuator/suspension result in further off-track oscillations when the actuator/suspension combination is commanded to hold stationary over the track.
In the invention, changes in the heretofore standard spaced-apart positional relationships of the suspension datum plane and the slider center of mass to one of coincidence in positional relationships reduces the lateral off-track motions of the slider write gap from sway forces encountered by the suspension. In one aspect, then, the invention changes the usual location of the suspension datum plane: extending outward in the plane of the conventional, single plane mounting plate, and thus spaced from the slider center of mass, to a suspension datum plane location determined by an angle made by a two plane mounting plate to bring the suspension datum plane to intersect with the slider center of mass. The former moment arm from the datum plane to the slider center of mass is reduced to zero length and sway forces are not multiplied as formerly. Center of mass of a slider herein refers to that locus where all the slider mass is apparently concentrated.
In another aspect of the invention, off-track motions of the slider gap from torsion forces encountered by the suspension are reduced by changing the usual spaced relationship of the dimple center of curvature and the slider gap horizontal plane to make them substantially coincident. Thus, the moment arm formerly existing by virtue of the spacing of the slider gap horizontal plane and the dimple center of curvature is also reduced to zero length and torsion forces are not multiplied as formerly.
Further, making the dimple longitudinal axis (an imaginary line about which the dimple extends, which line lies normal to the plane from which the dimple protrudes) substantially coincident with the vertical plane of the slider center of mass ameliorates slider gap reaction effect errors.
2. Description of the Related Art
Disk drives have within a close-fitting housing a motor and spindle, one or more disks on the spindle, one or more suspensions for each disk, each suspension comprising a load beam, actuators for shifting the suspensions over the disk(s), one or more read/write (RAN) heads and an aerodynamic carrier (typically being called a slider generally and in this description) carried by the suspension(s), and associated electronics, all assembled to pass a circular track of data repeatably under the R/W head so that data can be written to the disk and then accurately retrieved.
All the just mentioned components of a disk drive have design and manufacturing tolerance limitations and bring errors with them. Continual efforts on each component are being made to reduce the errors to as small a number and effect as possible.